In many instances, heavy industrial equipment utilizes one or more hydraulic rams to enable powered adjustment of the working implement or other element of the equipment under operator or automatic control. Specifically, for a number of years, road graders have utilized hydraulic rams to mount the grader blade or moldboard for height or cross-slope adjustment to meet the particular grading conditions. Quite recently, as described in detail in U.S. Pat. No. 3,346,976, issued to John Curlett and Raymond A. Gurries, road graders have incorporated automatic control mechanisms for such blade height and or cross-slope adjustments. More particularly, a fork is arranged to engage an external grade wire and actuate a hydraulic control valve for the hydraulic rams which effect raising or lowering of the blade to maintain it at desired grade level. In turn, to provide for automatic adjustment of cross slope of the blade, a pendulum unit is mounted on the road grader to actuate another hydraulic control valve for hydraulic rams that effectuate this purpose. Since the blade must be maintained at the desired level and cross-slope with a high degree of precision, the hydraulic control valves and other elements of the system must in turn be precise units capable of maintaining the desired level and cross-slope tolerances over extended periods of time. Severe problems, particularly in the case of the hydraulic control or servo valves have been encountered. Since certain mechanical tolerances in the valves must be in the neighborhood of 0.00001 inch to maintain the desired precision of hydraulic control, it will be obvious that but a slight amount of wear will create serious performance discrepancies. Thus, even though the hydraulic systems incorporate excellent filters, some minute particles (less than 3 microns) still remain and are sufficient to cause minute yet operationally significant abrasion of the relatively movable valve control surfaces. In addition, because of the pressures (e.g. 1,800 p.s.i) utilized in these hyraulic systems, any pressure imbalance in the valve may and does cause a minute but again significant scoring or chipping contact of critical control surfaces of the relatively movable parts of the valve. As a result, even though the valves are made with precision, their useful life under continued operation may be no more than 2 weeks. Not only is the valve replacement itself an expensive undertaking, but it also results in "down time" of the equipment to an extent which is of considerable economic impact.